SUMMARY OF THE BACKGROUND ART
As a next-generation alternative vehicle for internal combustion engine vehicles such as gasoline automobiles, an electric vehicle using a propelling electric motor is attracting attention. It is said that the electric vehicle which uses a clean electric energy can completely remedy the environmental problems such as harmful noises and exhaust gases, which are about 70% of the causes for the environmental pollution, derived from the internal combustion engine vehicles, and can extend by two times or more the resource life of fossil fuel such as petroleum.
The electric vehicle has propelling wheels which are suspended by shock absorbers from the vehicle body in the same way as a conventional gasoline automobile and is propelled by a power transmission device with an electric motor as the drive source. And, the electric motor has power supplied by an electric power unit.
Thus, the electric vehicle is quite different from conventional automobiles on the point that it has relatively heavy batteries. And, new issues are arising because of these batteries.
In other words, this electric power unit for supplying electricity to the electric motor has a plurality of storage batteries to form a battery power supply unit, and consists of a stability circuit for stably supplying output from the battery power supply unit, an electric motor for propelling, a motor drive circuit for directly controlling the motor revolution, and a control circuit for outputting a speed command or a torque command to the motor drive circuit. And, the motor-driven power from the motor is transmitted to the propelling wheels via a power transmission in the same way as a conventional vehicle.
As described above, the electric vehicle gets the motor-driven power from a plurality of batteries, and the performance of low-powered batteries becomes predominant, an expected traveling distance cannot be obtained, e.g., the electric vehicle cannot restart after temporarily stopping to wait at traffic lights, thus an unexpected stop is caused, possibly resulting in quite a danger. Therefore, a safety mechanism for the electric vehicle has been demanded to uniformly discharge the respective batteries while they are being used and to promote an efficient use of the electric power unit, thereby increasing a distance that the vehicle can travel.
On the other hand, it is advantageous to increase the battery capacity as much as possible in view of increasing mileage. But, when the electric power unit is compact and mounted close to the driver of the electric vehicle, especially an electric two-wheeled vehicle, insulation between the electric power unit and the driver is demanded as a safety mechanism for the electric vehicle.
And, the respective batteries of the electric power unit are recharged from an external power supply through a charging cord. It is quite dangerous if the electric vehicle moves while it is being recharged or moves without housing the charging cord even after finishing recharging. In view of the necessity of recharging the electric power unit, the structure around the charging cord is demanded as a safety mechanism for the electric vehicle.
As described above, the electric power unit is relatively heavy, and it is demanded to keep the stable running of the vehicle when the brakes are applied while it is running. And, since it is demanded to increase mileage as described above, it is advantageous to supply the electric power unit with regenerative electric power generated while braking. Thus, since the electric power unit is used, it is demanded to provide a regenerative brake and the stability of running as a safety mechanism for the electric vehicle.
Besides, the weight of the electric power unit cannot be disregarded in view of a weight balance, especially, in connection with the electric two-wheeled vehicle. Generally, the electric two-wheeled vehicle has a main stand, and it is demanded to make the vehicle stable when its stand is operated and to decrease an unsprung weight of wheels to provide stability while the electric two-wheeled vehicle is running as a safety mechanism for the electric vehicle.
Furthermore, since a drive circuit and a charger for the electric power unit generate heat due to charging and discharging as described above, it is demanded that their positions are decided in view of other devices and the batteries are detachable safely and easily for replacement or other purposes, as a safety mechanism for the electric vehicle. Detailed description will be made below.